1. Field of the Invention
This invention relates to an insulation displacement terminal which is so designed that, when a covered conductor (or electrical wire) is press-fitted into an insulation displacement slot, the internal conductor is brought into contact with the terminal without removal of the insulating cover of the covered conductor.
2. Background
FIGS. 4a to 4c show a conventional insulation displacement terminal disclosed by U.S. Pat. No. 4,385,794. More specifically, FIG. 4a is a perspective view of the insulation displacement terminal, FIG. 4b is a sectional view taken along line IVb--IVb, and FIG. 4c is a perspective view showing part of a covered wire connected to the insulation displacement terminal.
In FIG. 4, reference numeral 1' designates the aforementioned conventional insulation displacement terminal. The insulation displacement terminal 1' is formed integrally by pressing a piece of thin metal sheet which is punched. The insulation displacement terminal 1' includes an electrical contact section 2', engageable with a mating terminal, is formed at a front end portion thereof, a wire clamping section 3' formed at a rear end portion thereof, and an insulation displacement conductive portion 4' is formed at the middle portion between the front and rear end portions. More specifically, the electrical contact portion 2' is engageable with the mating terminal so as to be electrically connected to each other, the wire clamping section 3' has right and left retaining pieces (parts of the walls) 3a', which are bent inwardly to fixedly hold an insulating cover Wb of a wire W from the above, and the insulation displacement conductive section 4' is electrically connected to the conductor Wa of the wire W. The wire clamping section 3' is coupled through a first neck 6' to the insulation displacement conductive section 4', and the insulation displacement conductive section 4' is coupled through a second neck 7' to the electrical contact section 2'.
The insulation displacement conductive section 4' has a front insulation displacement portion 10A' and a rear insulation displacement portion 10B' which are arranged at the front and rear ends thereof. The front insulation displacement portion 10A' has a pair of right and left insulation displacement blades 11' and 11' which are confronted with each other in such a manner as to form an insulation displacement slot 12' between them into which the conductor Wb of the wire W is inserted. Similarly, the rear insulation displacement portion 10B' also has right and left insulation displacement blades 11' and 11' which are confronted with each other in such a manner as to form an insulation displacement slot 12' between them into which the conductor Wb of the wire W is inserted.
The wire clamping section 3', and the insulation displacement conductive section 4', and the electrical contact section 2' have a common bottom wall having the first neck 6' and the second neck 7'. The insulation displacement conductive section 4' is substantially U-shaped in section. More specifically, the insulation displacement conductive section 4' has a part of the bottom wall between the first neck 6' and the second neck 7', and right and left side walls 9' and 9' which extend upwardly from the right and left edge portions of the bottom wall, respectively. The insulation displacement blades 11' of the insulation displacement portions 10A' and 10B' are respectively formed by inwardly bending the front and rear end portions of the side walls 9'. The insulation displacement conductive section 4 has recesses 18 which are formed by pressing on the lines along which the side walls 9' are bent with respect to the bottom wall, so that the insulation displacement conductive section 4' is increased in bending rigidity.
The wire W is connected to the insulation displacement terminal 1' as follows. First, one end portion of the wire W is laid on the rear end portion of the insulation displacement terminal 1' in such a manner that the one end portion of the wire W is in parallel with the rear end portion of the insulation displacement terminal 1'. Under this condition, the one end portion of the wire W is pushed in the insulation displacement slots 12' of the insulation displacement conductive section 4 from the above. Accordingly, the right and left insulation displacement blades 11' cut the insulating cover Wb of the wire W, and contact the conductor Wa of the wire W. When the one end portion of the wire W is further pushed in, the conductor Wa is moved to be between the right and left insulation displacement blades 11', so that the conductor Wa is more positively held by the right and left insulation displacement blades 11'. In this operation, a force is applied to the right and left insulation displacement blades 11' so that the insulation displacement blades 11' are moved away from each other.
In general, an insulation displacement terminal is mass-produced, and a number of insulation displacement terminals are built in a connector housing in such a manner that they are adjacent to one another. Hence, there has been a strong demand for the provision of an insulation displacement terminal which is small in size, and light in weight. In order to decrease the weight of the insulation displacement terminal, it is essential to reduce the thickness of a metal plate which is formed into the insulation displacement terminal. And in order to miniaturize the insulation displacement terminal, it is necessary to decrease the width and the length of the insulation displacement terminal. For instance, in order to decrease the width of the insulation displacement terminal, it is essential to decrease the width of the insulating displacement blades forming the insulation displacement slot.
However, if the thickness of the metal plate, which is used to form the insulation displacement terminal, is decreased, or if the width of the insulation displacement blades is decreased, then the mechanical strength of the insulation displacement blades is also decreased, as a result of which, when the wire is pushed in the insulation displacement slot, the right and left insulation displacement blades are opened outwardly.
In view of the foregoing, in the conventional insulation displacement terminal 1' shown in FIGS. 4a to 4c, the insulation displacement blades 11' are respectively formed by bending inwardly the front and rear end portions of the side walls 9' of the insulation displacement conductive section 4'. However, the force, acting on the insulation displacement blades 11' when the wire W is press-fitted into the insulation displacement slots 12', acts collectively on the junctions (the bent portions) of the side walls 9' and the bottom wall. Therefore, there is a possibility that the side walls 9' are bent outwardly, and accordingly, the insulation displacement blades 11' are bent outwardly. In order to overcome this difficulty, the recesses 18' are formed on the junctions of the side walls 9' and the bottom wall. However, the recesses 18' are not so effective in preventing the falling of the upper end portions of the side walls 9'; that is, they are not so effective in preventing the insulation displacement blades 11' from being opened.
Furthermore, as shown in FIG. 4a, since an area in which the recesses 18' for reinforcing the side walls 9' is formed is restricted to the length of the insulation displacement conductive section 4' shown by an arrow A, there is a possibility that reinforcement for the side walls 9' can not be provided if it is difficult to form the recesses 18' in the area.